This chapter shall be known and cited as the "Lower Gwynedd Township Stormwater Management Ordinance."
The Township Board of Supervisors finds that:
(a) 
Inadequate management of accelerated stormwater runoff resulting from development throughout a watershed increases flood flows and velocities, contributes to erosion and sedimentation, overtaxes the carrying capacity of existing streams and storm sewers, greatly increases the cost of public facilities to convey and manage stormwater, undermines floodplain management and flood reduction efforts in upstream and downstream communities, reduces groundwater recharge, and threatens public health and safety.
(b) 
Inadequate planning and management of stormwater runoff resulting from land development throughout a watershed can also harm surface water resources by changing the natural hydrologic patterns, accelerating stream flows (which increase scour and erosion of streambeds and stream banks, thereby increasing sedimentation), destroying aquatic habitat, and increasing aquatic pollutant concentrations and loadings such as sediments, nutrients, heavy metals, and pathogens.
(c) 
A comprehensive program of stormwater management (SWM), including minimization of impacts of development, redevelopment, and activities causing accelerated erosion and loss of natural infiltration, is fundamental to the public health, safety, welfare, and the protection of the people of the Township and all of the people of the commonwealth, their resources, and the environment.
(d) 
Stormwater is an important resource by providing groundwater recharge for water supplies and baseflow of streams, which also helps to protect and maintain surface water quality.
(e) 
Impacts from stormwater runoff can be minimized by using project designs that maintain the natural hydrologic regime and sustain high water quality, groundwater recharge, stream baseflow, and aquatic ecosystems.
(f) 
Federal and state regulations require certain municipalities to implement a program of stormwater controls. These municipalities are required to obtain a permit for stormwater discharges from their separate storm sewer systems under the National Pollutant Discharge Elimination System (NPDES).
(g) 
Nonstormwater discharges to municipal separate storm sewer system (MS4) may contribute to pollution of waters of the commonwealth by the Township of Lower Gwynedd.
(h) 
The use of green infrastructure and low impact development (LID) are intended to address the root cause of water quality impairment by using systems and practices which use or mimic natural processes to (1) infiltrate and recharge, (2) evapotranspiration and/or (3) harvest and use precipitation near where it falls to earth. Green infrastructure practices and LID contribute to the restoration or maintenance of predevelopment hydrology.
The purpose of this chapter is to promote the public health, safety, and welfare within the Township by maintaining the natural hydrologic regime and by minimizing the harms and maximizing the benefits described in § 1241.102 of this chapter, through provisions designed to:
(a) 
Meet legal water quality requirements under state law, including regulations of 25 Pa. Code Chapter 93, to protect, maintain, reclaim, and restore the existing and designated uses of the waters of the commonwealth.
(b) 
Preserve the natural drainage systems as much as possible.
(c) 
Manage stormwater impacts close to the runoff source, requiring a minimum of structures and relying on natural processes.
(d) 
Provide review procedures and performance standards for stormwater planning and management.
(e) 
Focus on infiltration of stormwater to maintain groundwater recharge to prevent degradation of surface and groundwater quality and to otherwise protect water resources.
(f) 
Prevent scour and erosion of stream banks and streambeds.
(g) 
Provide for proper operation and maintenance of all stormwater management facilities and best management practices (BMPs) that are implemented within the Township.
(h) 
Provide standards to meet National Pollutant Discharge Elimination System (NPDES) permit requirements.
(i) 
Meet legal water quality requirements under state law, including regulations at 25 Pennsylvania Code Chapter 93.4(a) requiring protection and maintenance of "existing uses" and maintenance of the level of water quality to support those uses in all streams, and the protection and maintenance of water quality in "special protection" streams.
(j) 
Address the quality and quantity of stormwater discharges.
(k) 
Implement an illegal discharge detection and elimination program that addresses non-stormwater discharges into the Township's separate storm sewer system (MS4).
(l) 
Preserve and restore the flood-carrying capacity of streams.
(m) 
Minimize impervious surfaces.
(n) 
Address certain requirements of the Municipal Stormwater Sewer System (MS4) NPDES Phase II Stormwater Regulations.
(o) 
Implement the requirements of the Wissahickon Creek Watershed Act 167 stormwater management plan and the Neshaminy Creek Act 167 stormwater management plan.
The Township is empowered to regulate land use activities that may affect runoff, surface and groundwater quality and quantity by the authority of:
(a) 
Pennsylvania Municipalities Planning Code, Act 247, as amended.
(b) 
The Pennsylvania Stormwater Management Act, Act 167 of October 4, 1978 (PL. 864), as amended.
All regulated activities and all activities that may affect stormwater runoff, including land development and earth disturbance activities, are subject to regulation by this chapter. Regulated activities include, but are not limited to:
(a) 
Land development;
(b) 
Subdivisions;
(c) 
Prohibited or polluted discharges;
(d) 
Alteration of the natural hydrologic regime;
(e) 
Construction or reconstruction (refer to § 1241.202) of or addition of new impervious or semipervious surfaces (i.e., driveways, parking lots, roads, etc.), except for reconstruction of roads where there is no increase in impervious surface;
(f) 
Construction of new buildings or additions to existing buildings;
(g) 
Redevelopment;
(h) 
Diversion piping or encroachments in any natural or man-made channel; and
(i) 
Nonstructural and structural stormwater management best management practices (BMPs) or appurtenances thereto;
(j) 
Any of the above-regulated activities which were approved more than five years prior to the effective date of this chapter and resubmitted for municipal approval.
(a) 
Table 106.1 summarizes the exemptions from certain requirements in this chapter. "Proposed Impervious Surface" in Table 26-406.1 includes new, additional, or replacement impervious surface/cover. "Repaving" existing surfaces without reconstruction does not constitute replacement. The Township may deny or revoke any exemption pursuant to this section at any time for any project that the Township believes may pose a threat to public health, safety, property or the environment.
Table 106.1: Impervious Surface Exemption Thresholds
Proposed New Impervious
Chapter Article or Section
Type of Project
Less than 1,000 SF
1,000 SF to 5,000 SF
Greater than 5,000 SF
Article III, SWM site plan requirements
All regulated activities
Exempt
Not exempt
Not exempt
§ 1241.406, Nonstructural project design
All regulated activities
Exempt
Not exempt
Not exempt
§ 1241.407, Groundwater recharge
All regulated activities
Exempt
Not exempt
Not exempt
§ 1241.408, Volume control requirements
All regulated activities
Exempt
Not exempt
Not exempt
§ 1241.409, Stream bank erosion requirements
All regulated activities
Exempt
Exempt
Not exempt
§ 1241.410, Peak rate control requirements
All regulated activities
Exempt
Exempt
Not exempt
Erosion and sediment pollution control requirements
Must comply with Title 25, Chapter 102, of the Pa. Code and any other applicable state, county, and municipal codes
(b) 
Agricultural activities are exempt from the peak rate control requirements and SWM site plan preparation requirements of this chapter provided the activities are performed according to the requirements of 25 Pa. Code Chapter 102.
(c) 
Forest management and timber operations are exempt from the peak rate control requirements and SWM site plan preparation requirements of this chapter provided the activities are performed according to the requirements of 25 Pa. Code Chapter 102.
(d) 
Any aspect of BMP maintenance to an existing SWM system made in accordance with plans and specification approved by the Township is exempt.
(e) 
Infiltration exemptions.
(1) 
Depth to limiting zone. A minimum of two feet of soil suitable for infiltration must exist between the invert of the infiltration BMP and the top of the nearest limiting zone. Otherwise, the groundwater recharge requirement shall not be applied to the development site, and the entire volume must be treated.
(f) 
Hotspots.
(1) 
Stormwater hotspots. Appendix B[1] contains a list of types of hotspots that may be recognized by the Township. If a site is a potential hotspot, it has important implications for how stormwater is managed. First and foremost, untreated stormwater runoff from hotspots concentrated into a collection system shall not be recharged into groundwater where it may contaminate water supplies. Therefore, the volume control requirement shall not be applied to development sites that lie within a hotspot (the entire volume must still be treated). Second, a greater level of stormwater treatment shall be applied at hotspot sites to prevent pollutant wash-off after construction. The Environmental Protection Agency's (EPA) National Pollutant Discharge Elimination System (NPDES) stormwater program requires some industrial sites to prepare and implement a stormwater pollution prevention plan.
[1]
Editor's Note: The appendices are included as attachments to this chapter.
(2) 
Rate of infiltration. When infiltration is not feasible due to poor infiltration rates or hotspots, the water quality volume must be treated by an approved BMP(s).
(g) 
Additional exemption criteria:
(1) 
Exemption responsibilities. An exemption shall not relieve the applicant from implementing such measures as are necessary to protect public health, safety, or property.
(2) 
Drainage problems. Where drainage problems are documented or known to exist downstream of or could be expected due to the proposed activity, then the Township may deny exemptions.
(3) 
Exemptions are limited to specific portions of this chapter.
(4) 
HQ and EV streams. The Township shall deny exemptions in high-quality (HQ) or exceptional-value (EV) waters and source water protection areas (SWPA).
(5) 
For a development taking place in stages, the entire development plan must be used in determining compliance with these exemption criteria. The starting point from which to consider tracts as "parent tracts" in which future subdivisions and respective impervious area computations are cumulatively considered shall be the date of the municipal adoption of the original Lower Gwynedd Township Stormwater Management Plan Ordinance (Ordinance 434, June 21, 2005).
A. 
For example: If a property owner proposes a 300-square-foot shed after adoption of the municipal stormwater management ordinance, that property owner would be exempt from site plan and peak rate control requirements. If, at a later date, the property owner proposes to construct a garage and driveway adding an additional 1,300 square feet of impervious surface, the applicant would be required to submit a SWM site plan or small project SWM site plan demonstrating the stormwater control requirements for the total impervious surface of 1,600 square feet.
Any other ordinances, provisions or regulations of the Township inconsistent with any of the provisions of this chapter are hereby repealed to the extent of the inconsistencies only.
In the event that a court of competent jurisdiction declares any section or provision of this chapter invalid, such decision shall not affect the validity of any of the remaining provisions of this chapter.
Approvals issued pursuant to this chapter do not relieve the applicant of the responsibility to secure required permits or approvals for activities regulated by any other applicable code, rule, act, or ordinance, including Title 25 Pa. Code, Chapters 92, 102 and 105.
Notwithstanding any provision(s) of this chapter, including exemptions, any landowner or any person engaged in the alteration or development of land that may affect stormwater runoff characteristics shall implement such measures as are reasonably necessary to prevent injury to health, safety, or other property. Such measures also shall include actions as are required to manage the rate, volume, direction, and quality of resulting stormwater runoff in a manner that otherwise adequately protects health, safety, property, and water quality.
Any permit or authorization issued or approved based on false, misleading, or erroneous information provided by an applicant is void without the necessity of any proceedings for revocation. Any work undertaken or use established pursuant to such permit or other authorization is unlawful. No action may be taken by a board, agency, or employee of the Township purporting to validate such a violation.
The appendices listed below are incorporated herein by reference[1] as amended and shall be updated periodically as necessary by resolution of the Board:
(a) 
Appendix A, Stormwater Management Design Criteria.
(b) 
Appendix B, Hot Spots.
(c) 
Appendix C, West Nile Virus Guidance.
[1]
Editor's Note: The appendices are included as attachments to this chapter.
(a) 
If the Township determines that any requirement under this chapter cannot be achieved for a particular regulated activity, the Township may, after an evaluation of alternative, approve measures other than those in this chapter, subject to Subsections (b) and (c) in this section.
(b) 
Waivers or modifications of the requirements of this chapter may be approved by the Township if enforcement will exact undue hardship because of peculiar conditions pertaining to the land in question, provided that the modifications will not be contrary to the public interest and that the purpose of the chapter is preserved. Cost or financial burden shall not be considered a hardship. Modification may be considered if an alternative standard or approach will provide equal or better achievement of the purpose of the chapter. A request for modifications shall be in writing and accompany the Stormwater Management Site Plan submission. The request shall provide the facts on which the request is based, the provision(s) of the chapter involved and the proposed modification.
(c) 
No waiver or modification of any regulated stormwater activity involving earth disturbance greater than or equal to one acre may be granted by the municipality unless that action is approved in advance by the Department of Environmental Protection (DEP) or the delegated county conservation district.